It is vanishingly unlikely that he had never used the route
before if he was using it to "cycle home" at 2:15 am. It is
reasonable to suppose that he knew full well that this pedestrian
access had at least two flights of steps along its length (he'll
have been at least as aware as anyone else of the local changes
in level and the need for steps or ramps).

I don't think it is "vanishingly unlikely" that a person can know
about a route but has no reason to use it normally. It was the
middle of May and a warm night, after all, and probably no rush to
get home. It's a nice time to be out exploring...

...whilst around three times over the alcohol limit (for driving).
Yes - what could be more natural or normal than exploring in the
dark (which is exactly the point) whilst ...er ... inebriated?

Fortunately not everybody is like you.

I am surprised that you go sightseeing around your home area after
midnight in the dark whilst ****ed, but I have no choice but to
believe you... or something.

Some people like watching 22 men in fancy chase a leather ball round a
lawn. How weird.

That they do so is rather more credible than your thesis on
heavily-intoxicated cyclists sightseeing after midnight in their home
areas.

Is there a law that says that cyclists must go home after dark by the
shortest route?